Theme not fully responsive?

The theme does not appear to be fully responsive - for example on my page: https://mediapower.ca/our-services/web-design-for-businesses/  The header shows to be nicely responsive but the body is not when viewed on a mobile device. Even the videos - e.g. on the page: https://mediapower.ca/our-services/digital-video-for-businesses-and-professionals/corporate-video/ neither the page body nor the video is responsive on mobile devices. Could someone please advise. Thanks in advance. Pesi